Calcification mechanisms are being studied using the statolith synthesizing system of Aurelia. Intracellular vesicles are being examined ultrastructurally to determine their site of origin, and EM histochemical methods are being used to determine their chemical compositions. The effects of phosphate-containing compounds (pyrophosphate, diphosphonates, and cyclic AMP) as well as of hormone (thyroxine, PTH, CT, and GH) in statolith synthesis are being determined. Special attention is being paid to the possible roles of these compounds in affecting the uptake of ions, ion transportation in the statocytes, and the mineralization of calcification vesicles. Information concerning the role of cells in mediating calcification processes obtained from the jellyfish calcification model will be applied to problems of calcification in bones and teeth of higher organisms, including man. BIBLIOGRAPHIC REFERENCES: Spangenberg, D.B. 1976. Aurelia Metamorphosis: A Simple Model System for the Study of Thyroxine Action. NICHHD Symposium "Thyroxine and Brain Development," in press. Spangenberg, D.B. 1976. Intracellular Statolith Synthesis in Aurelia aurita. International Symposium on the Mechanisms of Mineralization in Invertebrates and Plants. U. of South Carolina Press, in press.